In avionics, sequencing a flight plan means determining the next flight plan segment (“leg”) which must be flown by an aircraft. When all the conditions are fulfilled, the aircraft will indeed fly this determined flight plan segment. In actual fact, a change of flight plan segment, which generally proceeds within the flight management system (FMS), is particularly tricky to determine. In an RNP AR (“Required Navigation Performance Authorization Required”) context, which is particularly demanding in respect of aircraft guidance, the sequencing operation may become particularly critical.
Various technical problems arise in respect of sequencing, which various known approaches are aimed at improving, but in a not totally satisfactory way.
Generally, the known FMS systems envisage the presence of several redundant sequencing systems. Comparison of the guidance commands then implies a necessary dependency between the various redundant entities of the system. This interdependency may lead to common errors and/or to the propagation of errors.
A known solution according to the prior art is described in patent document U.S. Pat. No. 8,660,715 which discloses a method and device for automatically monitoring air operations requiring a guarantee of navigation and guidance performance. The device described relies on a specific system, architectured according to a dual model (i.e. redundancy, with two independent navigation chains). In such an architecture, a fault in the system on one of its chains (or “sides”)—implying the undesired modification of the trajectory to which the aircraft is slaved—must be able to be detected and above all isolated so as to pursue the flight on the no-fault side. The approach described in the prior art comprises means for carrying out monitoring, so as to verify whether the two flight management systems in this specific configuration are in a condition to operate or to continue to operate in dual mode. This approach comprises limitations.
A need exists for advanced systems and methods for managing the sequencing of the flight plan of an aircraft.